Here's the trick: Boil your Russet potatoes with the skin ON.
Boil your potatoes whole, with the skin on. Pour off the hot water and replace with ice cold water before peeling (so you don't burn yourself). You can either peel with your hands, or grab a small paring knife and peel. The peels will come off fairly easily.
Healthier: Peeling your potatoes after they've been boiled is an easy trick to keeping in more vitamins, particularly Vitamin C. The peel reduces the amount of water the potatoes absorb, and the number of nutrients that are washed into your giant pot of water.
Creamier: Because the potatoes absorb less water when boiled with the peel on, they are able to absorb more of the liquid you choose to add in later. This means they will absorb more milk, chicken stock, cream, butter, or whatever else you want to add and those potatoes will be creamy instead of runny.
Note: Shocking the hot potatoes with ice cold water makes the outside skin cool enough to handle yet keeps the insides hot for your mashed potatoes.
For more information of why potatoes are a great nutritious meal option, how to prepare them, which types are best for which dishes, and more, head over here.